[Campbell Biology P.336] Achondroplasia is a form of dwarfism caused by a dominant allele. I... | Practice Question

Achondroplasia is a form of dwarfism caused by a dominant allele. If a man with achondroplasia Dd has a child with a woman of normal height dd , what is the probability that their child will have dwarfism?

  • A: 0%
  • B: 25%
  • C: 50%
  • D: 75%

Explanation

This is a monohybrid cross between a heterozygote Dd and a homozygous recessive dd , as shown in the Punnett square in Figure 14.18. The possible offspring genotypes are Dd and dd. The Dd genotype results in dwarfism. Therefore, there is a 1/2, or 50%, chance of having a child with the dominant phenotype.